81871657 has 4 divisors (see below), whose sum is σ = 93567616. Its totient is φ = 70175700.

The previous prime is 81871633. The next prime is 81871679. The reversal of 81871657 is 75617818.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81871657 - 2¹⁹ = 81347369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81871607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5847969 + ... + 5847982.

It is an arithmetic number, because the mean of its divisors is an integer number (23391904).

Almost surely, 2^81871657 is an apocalyptic number.

It is an amenable number.

81871657 is a deficient number, since it is larger than the sum of its proper divisors (11695959).

81871657 is a wasteful number, since it uses less digits than its factorization.

81871657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11695958.

The product of its digits is 94080, while the sum is 43.

The square root of 81871657 is about 9048.2958063936. The cubic root of 81871657 is about 434.2213701448.

It can be divided in two parts, 81871 and 657, that added together give a palindrome (82528).

The spelling of 81871657 in words is "eighty-one million, eight hundred seventy-one thousand, six hundred fifty-seven".